MOSCOW: Saudi and Russian foreign ministers, Adel al-Jubeir and Sergei Lavrov, will meet in Moscow on Tuesday to discuss global energy markets and the Middle East crisis, including the war in Syria and the threat of Islamic State, Russia's foreign ministry said.

Jubeir will visit Moscow just a week after the two met in Doha and held three-party talks with US Secretary of State John Kerry amid intensified high-level diplomatic contacts over Syria and Islamic State.

Diplomacy has so far failed to end the war in Syria as Russia and Iran back Syria's President Bashar al-Assad, while the United States, its ally Saudi Arabia and other regional countries support rebels seeking to oust him.

Lavrov said after his latest meeting with Kerry that Moscow and Washington were unable to overcome that point of contention and could not agree on how to jointly fight Islamic State, which captured swathes of Syria and the neighbouring Iraq.

Lavrov and Jubeir will also discuss "closer coordination on global energy markets", the ministry said, an important theme for Russia, which is one of the world's biggest oil producers and is going through a painful economic downturn.

Low oil prices are hurting Russia's budget and Moscow has held regular meetings with OPEC members, including Riyadh, on the matter.

But the cartel has focused on defending market share rather than propping up the price, with its oil output reaching the highest monthly level in July.